Manufacturing Bits: Nov. 8

The ink can be used to print inexpensive electrochemical devices, such as batteries, sensors, textile-based electrical circuits and other products. A key to the technology is the self-healing concept. This means a device could autonomously repair itself in the field.

Over the years, the industry has developed self-healing materials. But they require an external trigger to start the process. And the self-healing process could range anywhere from a few minutes to several days.

Researchers from the University of California at San Diego use a technique to print the ink on a surface or object. The ink is based on magnetic microparticles. The material itself is neodymium, a soft, silvery metal. In the process, the microparticles orient themselves in a certain way via a magnetic field. But at the same time, a trace or other part of the desired object could become damaged or torn during the process.

But due to the magnetic properties of the materials, the tears are magnetically attracted to one another. This, in turn, causes the tears to heal themselves. This self-healing process can occur at speeds around 50ms. It can repair tears as wide as 3 millimeters without any user intervention or external trigger.

“Our work holds considerable promise for widespread practical applications for long-lasting printed electronic devices,” said Joseph Wang, director of the Center for Wearable Sensors and chair of the nanoengineering department at UC San Diego.

This technology enables the development of customized and precise magnets in specific pre-determined shapes. The development of magnetic sensors is one application for this technology.

Traditionally, 3D printers generate plastic structures. In contrast, a magnetic printer uses a filament of magnetic micro granulates. These granulates are held together by a polymer binding material.

In TU’s technology, the printer heats the material. A nozzle then creates an object, which is 90% magnetic material and 10% plastic. Finally, the object is exposed to an external magnetic field. This, in turn, converts it into a permanent magnet.

A magentic cup-like shape, created in the 3D-printer. (Source: TU Wien)

“The strength of a magnetic field is not the only factor,” said Dieter Süss, head of the Christian-Doppler Advanced Magnetic Sensing and Materials laboratory at TU Wien, on the university’s Web site. “We often require special magnetic fields, with field lines arranged in a very specific way – such as a magnetic field that is relatively constant in one direction, but which varies in strength in another direction.”

Süss added: “This method allows us to process various magnetic materials, such as the exceptionally strong neodymium iron boron magnets. Magnet designs created using a computer can now be quickly and precisely implemented–at a size ranging from just a few centimeters through to decimeters, with an accuracy of well under a single millimeters.”